Sith Loyalists were those that choose to support the Ni'novian Republic prior to the Sith Revolution. They supported the idea of a democracy and the status quo as opposed to the revolutionary Imperialists. The main supporter of this group was Scyrone and supporters included Boran, Tress, and Jaden Mustik. Kracor was also in support of the Loyalists, but was more secluded and focused on his own goals.
The Loyalists prepared to fight the Imperialists when Jaden's defection turned the tide. Instead of a civil war or even two separate governments, the Imperialists seized political power in the Council and impeached Scyrone on several charges both true and trumped up. That was the end of the Loyalist movement as the Ni'novian Republic gave way to the Order of Sovereignty in a bloodless revolution.